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Adam Koch board concept explanation

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nico34
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Adam Koch board concept explanation

Postby nico34 » Sun Mar 01, 2015 12:27 am


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davesails7
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Re: Adam Koch board concept explanation

Postby davesails7 » Sun Mar 01, 2015 2:48 am

The description of how the board reacts after crashing down seems like he is describing two very different things. He says the board pierces the surface and dives in like a bird (which I can see would happen with this shape), but then he says that it just skips right off the surface (which I can't see how that would happen with this shape).

I also don't understand the part about planing boards getting stuck to the water surface. If you go to pick up a surfboard that's floating in the water, there's no noticeable force holding it to the water (other than gravity). Nothing compared to the foil having to lift your body weight at least.

Glad to see someone trying something different though. This idea doesn't make sense to me, but hope it works out for him. Just a few years ago, general knowledge was that foils were not as fast as raceboards around a course, but luckily some people didn't believe that and kept trying new things :thumb:

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Re: Adam Koch board concept explanation

Postby uncool » Sun Mar 01, 2015 10:25 pm

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Last edited by uncool on Mon Mar 02, 2015 6:46 am, edited 1 time in total.

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Re: Adam Koch board concept explanation

Postby plummet » Sun Mar 01, 2015 11:14 pm

davesails7 wrote: I also don't understand the part about planing boards getting stuck to the water surface. If you go to pick up a surfboard that's floating in the water, there's no noticeable force holding it to the water (other than gravity). Nothing compared to the foil having to lift your body weight at least.

:
He's talking about surface tension, and resistance to move through the water.

I'm not sure how to explain it properly. But water is sticky. Use your surfboard analogy. Pick it up on the beach and you feel no resistance to pick it up apart from its weight. Pick the same board up in the water and you need to exert more force to pick it up. To break the surface tension of the water holding on to the board.

I had a dramatic example of this when i learnt to kite kitesurf after years of kitelandboarding. I was used to crouching down and jumping up when sending the kite to jump. When I tried the exact same technique on the water the board stayed stuck to the water..... WTF!?! I had to learn to slice it out of the water.

So.... What he is saying is that is moth copy structure has a similar bouancy to a normal board but considerably less surface area than a standard board. So... When normal board with all that surface area hits the water it will be slowed down faster (needs to displace more water) than his design. Thus the sticky reference. It makes sense to me.

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Re: Adam Koch board concept explanation

Postby zloilyoha » Sun Mar 01, 2015 11:37 pm

davesails7 wrote:
I also don't understand the part about planing boards getting stuck to the water surface.
maybe foil starts to plane much earlier then a board - so when the board is not on its plane and foil want to rise it up over the water its realy stucking?

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davesails7
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Re: Adam Koch board concept explanation

Postby davesails7 » Mon Mar 02, 2015 12:32 am

plummet wrote:I'm not sure how to explain it properly. But water is sticky. Use your surfboard analogy. Pick it up on the beach and you feel no resistance to pick it up apart from its weight. Pick the same board up in the water and you need to exert more force to pick it up. To break the surface tension of the water holding on to the board.
I'll try this out next time I'm out at the beach. How much extra force do you think it takes to lift a 5' x 21" board off the water? I can't see it as significant compared to the foil having to lift your body weight (minus some from the lift of the kite). I feel like any suction is going to be broken anyway with the board on an angle (both fore-aft and side-side) or by any chop. I'll give it a try though.

I'll try to look for it when foiling also, but I can't remember ever feeling like the board was sticking to the water and stopping me from lifting off.

Also, when you are planing, there is a high pressure on the bottom of the board lifting you up. That's why a small thin twintip can support you even though it has only a few pounds of buoyancy. Displacement hulls (like this) running at high speeds (for their length) tend to suck down into the water.
plummet wrote:So.... What he is saying is that is moth copy structure has a similar bouancy to a normal board but considerably less surface area than a standard board. So... When normal board with all that surface area hits the water it will be slowed down faster (needs to displace more water) than his design. Thus the sticky reference. It makes sense to me
I don't think buoyancy is going to be enough force to lift the nose back up when it comes crashing down. There just isn't much volume in the nose. It might not have much resistance when it first hits the water, but it's also not going to have any upward force to bring the nose back up. You really need the projected area up in the nose to lift it back up after it crashes down.

Also there is still a lot of wetted surface area, it's just that the area is on the sides instead of the bottom.

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Re: Adam Koch board concept explanation

Postby cleepa » Mon Mar 02, 2015 9:08 pm

The videos of the board in action are pretty uninformative. All you see is a few waterstarts, the board in the air as normal and one crash.


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